Although the final price is shy of the original asking price of $190 million, the sale is still notable. It topped the $117.5 million sale of a nine-acre Silicon Valley estate, but fell shy of a $132.5 million sale of Montana's Broken O Ranch. However, according to Curbed.com, many consider the Montana property to be a working farm, not a single-family home. Under that standard, Copper Beech becomes the most expensive single-family home ever sold.

It was easily the most expensive residential transaction in Greenwich's history, more than doubling the $45 million paid for the 80-acre mid-century horse farm at 25 Lower Cross Road in 2004, which previously held the distinction, according to the Greenwich Time. Like Copper Beech Farm, that property was also listed by Realtor David Ogilvy.

Top ZIP codes for mega-mansions

Beverly Hills led the nation in sales of homes of $10 million or more last year, reports CNBC's Robert Frank.

The mansion, located along the Greenwich waterfront, was once home to Harriet Lauder Greenway, Andrew Carnegie's niece. After the death of her son in 1981, the property was purchased by timber tycoon John Rudey, who had a portion of the property classified as a forest.

The buyer, who purchased the home through a limited-liability company, is unknown.